<html>
    <head>

    </head>
    <body>
        <input type="text" id="input1"><br>
        <input type="text" id="input2"><br>

        <script>
            input1.onkeydown=function(e){
                console.log("按下");
                console.log(e.key);
                console.log(e.keyCode);
            }

            input1.onkeyup=function(e){
                console.log("抬起");
                console.log(e.key);
                console.log(e.keyCode);
            }

            input1.onkeypress=function(e){
                console.log("按了");
                console.log(e.key);
                console.log(e.keyCode);
            }



            input2.onkeydown=function(e){
                if(e.keyCode>=48&&e.keyCode<=57){

                }
                else{
                    console.log("不是数字");
                    event.preventDefault();
                }
            }
        </script>
    </body>
</html>